Picture a church tower with bats ping-ponging around - that's the mental image for thoughts bouncing off the walls of a frazzled mind and the inspiration for the idiom Bats in the Belfry. This verbal gem first dropped in 1899 when a writer tried to describe a chaotic opera scene. Before long, the phrase caught on, with other authors adopting it to denote anything from mild quirkiness to full-blown lunacy.

Whether it's your colleague's wild new business idea or your own late-night inspiration to reorganise your entire life, 'bats in the belfry' fits the bill. Since its inception, this batty phrase has taken flight in popular culture, inspiring song titles and movie names. It even made a surprise cameo in a 2012 Teenage Mutant Ninja Turtles episode.